Electrical signaling system



April 1939- P. F. G'UNNING 2,154,742

ELECTRICAL SIGNALING SYSTEM Filed Oct. 14, 1936 f/v VEN TOR Faker FRANKGUNN/NG ATTY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE ELECTRICAL SIGNALINGSYSTEM ware ' Application October, 14, 1936, Serial No 105,460

In Great Britain November 5, 1935 11 Claims.

The present invention relates to signaling systems for the remotesupervision of'the condition of circuit breakers or the like. located atan electric power substation and is particularly suitable for signalingto a central point from a plurality of substations. For example, in alarge electric power network comprising a number of substations, it isnot usually a commercial proposition to indicate automatically overpilot wires the oil circuit breaker positions from all substations owingto the prohibitive cost of the pilot lines and equipment required; noris it a commercial proposition to have the smaller substationscontinuously staffed, principally on account of these stations beinggenerally in the majority.

The chief object of the invention is to provide a simple and cheapapparatus which can be associated with the ordinary telephone at aremote substation thus obviating the need of special signaling channelsto the control centre. The arrangement is preferably such that if whenthe substation is called there is no verbal reply due to the absence ofan attendant-an audible signal will be returned to the caller whichsignal in addition to giving an indication of the condition of equipmentat the substation may also indicate to the caller which substation isresponsible for the signal. At the same time the association of theindicating apparatus with each substation telephone neither interfereswith nor reduces the efficiency of the telephone system as a whole. Itshould be mentionedthat the term substation has been used forconvenience to cover any point wheregeneration, transformation and/orcontrol of electric power may be effected.

According to one feature of the invention in a signaling system for theremote supervision of the condition of circuit breakers or the like atan electric power substation the supervisory circuit is completed inresponse to the setting up of a connection over the regular tele phonenetwork.

According to another feature of the invention the necessary informationis transmitted by audible signals over a line equipped for telephonyover the regular exchange network.

A further feature of the invention is that apparatus responsive to analteration in the condition of the equipment at the substation causes acall to be set up over the regular telephone network to give warning ofsuch alteration.

According to still another featureof the invention an electric powersubstationis provided with equipment which is set in operationresponsiVe to an incoming telephone call which is not answered within apredetermined time and thereupon transmits audible signals to thecalling party to indicate the condition of the circuit breakers or thelike at the substation.

The invention will be better understood from the following descriptionof one method of carrying it into effect reference being had to theaccompanying drawing which shows, in Fig. 1, a circuit diagram of theapparatus in association with the telephone instrument at a substation.

Fig. 2 shows a circuit diagram of the apparatus used in connection withthe circuit breakers to control the transmission of tone pulsesindicative of the condition of the circuit breakers.

In the arrangement shown, facilities are also provided whereby a changein the condition of any of the equipment concerned may be auto maticallyindicated at the telephone exchange even though no call is put throughto the substation. It will be appreciated that if this latter facilityis not required, the circuit can be still further simplified.

The direct current supply foroperating the equipment is shown bypositive and negative symbols in a circle and may be any convenientvoltage preferably obtained from a battery so that it would still beavailable if the main power supply shouldfail. It should also bementioned that since relay OCB is normally operated the armatures ocbland 00112 of this relay have been shown in operated position. Theswitches D, comprising the magnet DM and bank sets DI, D2 and D3, and Scomprising the magnet SM and bank sets SI, S2, S3, and S4, which are ofthe electromagnetically operated step by step type used in telephonesystems have been shown as having 25 contacts which is a usualconstruction but it may be more convenient in practice to provide themwith two sets of single ended wipers located at 180 so as to give theeiiect of a 50-point switch.

For the purpose of the description it will be assumed first that thesubstation is unattended andthat a call is put through to it from thecontrol centre. When ringing current is applied at the exchange to thetelephone line the telephone bell BL will be rung while at the same timerelay ST will be operated in parallel by way of condenser .QA. Thisrelay is conveniently shunted by a rectifier MRA to enable an ordinarytelephone type relay to operate satisfactorily on alternating current.Relay ST upon operating, at armature stl operates relay A which in turnoperates relay B. The latter relay then at armature bi energises themagnet SM of the switch S which is of the reversedrive type andtherefore does not move its wipers on energisation of the magnet. Theinterrupter contacts cm are opened however and accordingly the operatingcircuit of relay A is disconnected. Relay A thereupon releases after aslight interval and in turn releases relay B, which after .a furthershort interval de-energises the magnet SM whereupon the wipers areadvanced to position 2. Positive is then extended over wiper SE tore-operate relay A and the interaction between relays A and B and magnetSM is repeated and causes the wipers to be advanced step-by-step roundthe bank at a speed of the order of five steps per second or less, thisspeed being controlled by the copper slugs on the two relays.

When the wipers of switch S reach position 25 the magnet DM of theswitch D is energised over wiper S2 in parallel with magnet SM fromarmature b I and on release of relay B, the switch S is advanced toposition i while the switch D is advanced to position 2. Positive is nowextended over wiper D3 to operate relay SS which at armature ss2 bridgesthe winding of the transformer T directly across the line in order totrip the ringing at the telephone exchange and at armature ssl preparesa circuit for the self-interrupted tone generating relay TR. Relay STreleases due to the cessation of ringing current but the switch Scontinues to step since relay A is re-operated in position I by way ofwiper DI in position 2. The first rotation of the switch S is thus usedto time an interval during which the station attendant may answer thetelephone and pass on the information verbally. If however the telephoneis unanswered during this period, then on the second and subsequentrotations of the switch S, tone indicating signals will be impressed onthe incoming telephone line in a manner now to be described.

It will be seen that bank contacts engaged by wipers S3 and S4 are wiredto a cross-connection frame, to which are also wired signaling contactson the equipment to be supervised, in this case, three oil circuitbreakers. During each rotation of the switch S positive potential pickedup by wipers S3 or S4 will operate relay P and since relay SS is nowoperated, armature pl will on each operation energise the tone relay TRfrom the local dry battery BA and an audible tone will be impressed byinduction through the windings of the transformer T on to the line andthus transmitted to the calling party. If relay P is operated over wiperS3 a pulse of tone will be sent out for the full period during which thewipers are resting in that position while if it is operated over wiperS4 tone will be sent out only for the period during which relay A isoperated, which period represents approximately half the time the wipersremain in each position. It will be assruned by way of example that thecode signal representing the particular substation responsible for thesignal comprises three dots or short pulses of tone. An indication willthen be given of each circuit breaker in turn, a dash or long pulsebeing transmitted when a particular breaker is in a closed positionwhile a dot is transmitted if it is in a tripped or open position. Thewhole cycle for this particular substation with the first and thirdbreakers closed and the second breaken open would thus be:dotdot-dotsilence-dashsilence-dot silence dash, this cycle beingrepeated for any predetermined number of times in a manner to bedescribed later.

Accordingly on this assumption contacts 8, I6 and 24 in the bank ofwiper S3 are cross-connected to signaling contacts of the breakersconcerned and contacts I, 2, 3, 8, l8 and 24 in the bank of wiper S4 areconnected to positive. Thus on rotation of the switch wipers relay Pwill be operated over wiper S4 for the operated time of relay A on eachof the first three steps thus transmitting the station identificationsignal consisting of three short pips of tone to the calling party. Inposition 8 since breaker 0013! is closed, a long pulse of tone will betransmitted, in position I6 since breaker OCB2 is open a short pulse istransmitted while in position 24 a long pulse is transmitted sincebreaker OCBS is closed.

It will be seen that with the arrangement described the switch S servesto control the initial delay period and also the actual sending of thesupervisory signals. By simple alterations of the strappingarrangements, any variation of the code combination and any desiredrelation be tween the lengths of the long and short pulses can beeffected. Thus by arranging that each marking in the bank of wiper S3occupies two strapped contacts, the long pulse can be made much greaterthan the short pulse, though it would then be necessary to employbridging type wipers to prevent disconnection of the pulse during thetransit time between contacts. Each breaker indication might, moreover,be preceded by a number of short pulses corresponding to the breakernumber, thus preventing any possible confusion.

When the switch S after its second rotation reaches the last position,the magnet DM will be energised in parallel with the magnet SM as abovedescribed and the sending operation of the switch S will be repeated.After any predetermined number of rotations as determined by thestrapping of the bank of wiper DI it will be seen that the switch D inmaking a further step will disconnect the circuit for relay A at itswiper DI thus arresting the motion of the swich S in position I, whilethe switch D then homes in a self-interrupted circuit over the remainingstrapped contacts on its bank DI. Relays A, B and SS will now releaseand the indicating equipment at the station will then be restored tonormal and will send no further impulses to the caller unless he hangsup and re-calls or unless a circuit breaker now changes position. Therepeat facility provides a check in case signals are lost ormisconstrued on the first cycle.

Considering now a call when the substation is attended, the bell will berung and relay ST will be operated as before and will initiate theoperation of the switch S in the normal manner and this advancesstep-by-step to time the delay period. If the attendant answers the callbefore the lapse of this period, the switch-hook contacts SH complete adirect current circuit to the exchange and this trips the ringingwhereupon relay ST releases. Relay CO which is arranged to benon-operative in series with the bell and relay ST in response toringing current, now opcrates and extends positive over wiper D3 inposition I to operate relay P which at armature p2 cuts off any circuitfor the magnet DM when the switch S reaches the last position. Theswitch S continues to rotate under the control of relays A and B untilit reaches position I when there will be no re-energising circuit forrelay A and the switch will be stopped. The station attendant in themeantime may pass verbal information on to the calling party. On releaseof the connection, relay CO releases and releases relay P and theequipment is again restored to normal.

In case one of the breakers changes position, its indicating contactswill be operated and during the transit time of the contacts in thechain holding circuit for relay OCB, this relay will release. In thealternate position of the contacts a holding circuit is again preparedfor relay OCB, since the contacts are closed in both positions of thebreaker. Relay OCB upon releasing, at armature ocbl further disconnectsits holding circuit and extends positive over Wipers D2 and SI inposition I to energise relay A. This relay thereupon starts up theswitch S in the normal manner and also each time relay A operates acircuit is completed over armature a3 operated, and armature ocb'2normal to operate relay SS. Relay SS therefore pulses in synchronismwith relay A and at armature 882 the left-hand winding of thetransformer T is intermittently bridged across the line thus causing thecalling lamp at the exchange to flash. This warns the telephone operatorthat there has been a change in the condition of the equipment at thestation and she will inform the control centre. Thereupon a call is putthrough to the station in the usual manner in order to ascertain theactual condition prevailing. When the witch S reaches the last position,the magnet DM is energised over wiper S2 and hence when the switch Ssteps to position I the switch D will be stepped to position 2 in thenormal manner. The switch S will commence to rotate a second time butrelay SS will now be maintained operated over wiper D3 and the flashingof the operators calling lamp will thus be stopped but a steady callingsignal will be maintained. If the operator challenges the line, she willhear the tone indications transmitted by the pulsing of relay P. Afterthe predetermined number of rotations of the switch S, the switch D willhome and the switch S will be stopped in the normal position and relaysA, B and SS will be released. At armature ssZ the calling signal willnow be removed from the main exchange.

It will be understood that if the telephone exchange operated on theautomatic principle instead of on the manual principle as above assumed,comparatively small alterations to the equipment would be necessary toenable it to send a train of impulses corresponding to the digit orother code ordinarily used for calling an operator. Moreover theequipment could be arranged to send out the call number of the controlcentre and transmit the indicating tone signals only when the call wasanswered though this would involve some increase in the complexity andexpense of the equipment.

The tone generating arrangement suggested above using a separate drybattery may be replaced by the use of a tone transformer, the secondarywinding of which can be connected across the line at will While theprimary is associated with a tone generating relay operated from thesignaling equipment battery. Since however it is necessary to isolatethe high voltage equipment from the telephone lines as indicated by thedotted line insulation would have to be provided between the transformerwindings and this arrangement might therefore prove more costly than themethod described.

Wiper S2 and its associated bank are only effective in one position andmight therefore be replaced by cam operated contact springs which couldbe arranged to close only when the wipers are set in the last position.

It will be understood that the supervision need not be confined tobreakers but could be arranged to give information about isolators,relay flags, water level, winding temperature, meter readings,transformer taps, protective pilot conditions, battery conditions,voltage, current, power, water pressure, gate positions, valve positionsand other data.

By variation of the tone frequency or of the length of time during whichthe supervisory tone is applied to the line the audible signals can beused for quantitative as well as qualitative supervisory indications.Again, the system can be arranged so that the supervisory telephone caninitiate equipment tests or operations at the called s'tation'and theresults of these tests or operations can be indicated back to thecalling party in the form of audible supervisory signals.

The arrangement described transmits the audible tone signals apredetermined number of times but as an alternative the signaling couldbe stopped by the arrival of a further call or by the transmission of atone or other signal from the calling party.

It will thus be seen that with the system according to the invention thefacilities of all stations so equipped are available at all telephoneson the telephone system and thus in times of trouble when a controlengineer is busy, information as to what has happened at a substationmay be obtained by other engineers on other telephones thus relievingthe control engineer and the tramc on his control telephone. Furthermorethe control engineer by simply making a call to a station may ascertainwhether the telephone line to the station is good or otherwise thusproviding a simple and cheap form of pilot test. In practice thisadvantage is considerable as the distant station. may be unattended andthe prevailing safety regulations may demand that a telephonemaintenance ofiicial shall only obtain access to the station whenaccompanied by one of the power authoritys engineers.

What is claimed is:

1. In a power supervisory system, a power substation, a telephone lineconnecting said substation with a central office, a tone genera-tingdevice at said substation, indicating contacts at said substationcontrolled by circuit breakers, means eifective upon the expiration of apredetermined time interval for rendering said tone generator effectiveto transmit a. characteristic series of tone pulses over said line foridentifying said substation, and means coacting with said indicatingcontacts for transmitting another characteristic series of tone pulsesfor indicating the condition of said circuit breakers.

2. In a power supervisory system as claimed in claim 1, a step-by-stepswitch, and means controlling said switch to measure the predeterminedtime by the advance of said switch through a given number of steps.

3. In a power supervisory system as claimed in claim 1, a step-by-stepswitch, means for controlling said switch to measure the predeterminedtime by the advance of said switch through a given number of steps, andmeans eifective upon the. termination of said predetermined timeinterval for connecting said switch to control the transmission ofaudible signals over said line.

4. In a power supervisory system as claimed in claim 1, a step-by-stepswitch, means for controlling said switch to measure the predeterminedtime by the advance of said switch through a given number of steps,means effective upon the termination of said predetermined time intervalfor connecting said switch to control the transmission of audiblesignals over said line, and means for terminating the transmission ofsaid audible signals after said signals have been transmitted apredetermined number of times.

5. In a telephone system, a telephone substation, a line connecting saidsubstation with a central ofiice, switching devices at said substationeach having an open and a closed position, and means responsive to achange in position of one of said switching devices for transmitting aseries of pulses over said line.

6. In a. signaling system, a telephone line, a tone generator, means forcontrolling said generator to transmit tone pulses of variable durationover said line, indicating contacts controlled by a switching devicehaving a closed and an open position, means for operating said firstmeans to transmit a tone pulse having a definite duration over said linewhen said indicating contacts are in their closed position, and meansfor operating said first means to transmit a tone pulse having adifferent duration over said line when said indicating contacts are intheir open position.

'7. In a signaling system, a telephone line, a tone generator, means forcontrolling said generator to send tone pulses of variable duration oversaid line, indicating contacts having a closed and an open positioncontrolled by a switching device, a first circuit for operating saidmeans including said indicating contacts, a second circuit for operatingsaid means in multiple with said first circuit, means for closing saidfirst circuit for a definite time interval with said contacts in theirclosed position, and means for closing said second circuit for adifferent time interval.

8. In a signaling system, a telephone line, a tone generator, indicatingcontacts controlled by a switching device having a closed and an openposition, a first circuit including said indicating contacts, a secondcircuit in multiple with said first circuit, and means controlled oversaid circuits for controlling said tone generator to trans:-

mit tone pulses of variable duration over said telephone line.

9. In a signaling system, a telephone line, a tone generator fortransmitting a tone pulse of variable duration over said line,indicating contacts, one circuit associated with the generator and saidindicating contacts for controlling the transmission of said pulse for adefinite time interval, and another circuit similarly associated forcausing a prolonged transmission of said pulse in accordance with aparticular position of said indicating contacts.

10. In a supervisory system a substation, a telephone line, a centraloffice having means for calling said substation over said line, a tonegenerating device at said substation, indicating contacts at saidsubstation, means at said substation operated at a predetermined timeafter said substation. has been called for operating said tone generatorto transmit a characteristic series of tone pulses over said line foridentifying said substation, and thereafter coacting with saidindicating contacts for transmitting characteristic tone pulses oversaid line for identifying the condition of said contacts.

11. In a supervisory system, a. substation having an automaticresponding device, a telephone line, means controlled over said line forsignaling said substation, means in said device operated through acomplete cycle when the substation is signaled for measuring a timeinterval, said means reoperated upon termination of said cycle forcausing the transmission of a distinctive series of tone pulses oversaid line for identifying said. substation.

PERCY FRANK GUNNING.

